1. Field of the Invention
The present invention relates to improved methods and related solutions for effecting enhanced penetration of wood preservatives through the use of buffered amine oxides in combination with alkoxylated oils and also relates to such systems effectively employed with wood which has been stiffened through removal of water therefrom.
2. Description of the Prior Art
It has been known to enhance penetration of wood preservatives into wood through the use of amine oxides combined with buffering agents to achieve a synergistic effect which causes a wood preservative to penetrate the wood to a greater depth. See, for example, U.S. Pat. Nos. 7,655,281; 7,896,960; 9,125,398 and 9,125,399, the disclosures of which are expressly incorporated herein by reference. These patents disclose methods of protecting wood through enhanced penetration of wood preservatives by providing a solution which includes at least one amine oxide, at least one organic wood preservative and a buffering agent. The buffering agent is selected from a group consisting of borate and non-borate based buffering agents. When combined with amine oxides, these enhance the penetration of useful materials into wood.
When wood has been forcefully over dried through kiln conditioning, or unusual ambient climatic conditions, the resulting wood is difficult to penetrate through conventional methods of wood preservation, including mechanical pressure-vacuum impregnation. This overdrying results from water being removed from the wood which causes the wood to become stiffened. There are, in principle, the water may be present in the form of just capillary retention or by loose chemical bonding by hydrogen or by molecular retention. Treating the wood to remove water from one or more of these sources results in the stiffening of the wood. This stiffening of the wood not only improves the structural strength of the wood and enables certain woods so processed to be employed in uses such as building construction wherein, without such stiffening, a specific wood would not have had adequate strength to satisfy building codes and function effectively. The artificially stiffened wood is a result of the pits being closed resisting effective penetration of wood preservative solutions into the woods. The pits can vary in structure related to the specific wood specie, but all are believed to contain a membrane formed from the middle lamella of the cell wall in between adjacent cell walls. These pit membranes are understood to be the major obstacle to efficient penetration of wood preservatives.
The three forms of water contained in wood are: 1. Free water, the bulk of the water contained in the cell lumina is retained only by capillary forces. It is bound chemically and is called “free water”. Free water is not the same thermodynamic state as liquid water as energy is required to overcome the capillary forces. Also, free water may contain chemicals thereby altering the drying characteristics of the wood. 2. A second category of water would be bound or hygroscopic water. This is bound to the wood by way of hydrogen bonds. The attraction to wood of free water arises from the presence of the three hydroxal groups (OH) in the hemicellulose and lignin molecules in the cell wall. The hydroxal groups are negatively charged and as water is a polar liquid, the free hydroxal groups in the cellulous are trapped and hold water by hydrogen bonding. 3. Water is also present in the cell lumina in the form of water vapor, but this is normally negligible at normal temperature and geminity.
There remains, however, a need for improved methods and solutions for effectively delivering wood preservatives to an enhanced depth even with respect to hard to penetrate woods such as forcibly overdried woods.